Chevrolet Repair: vacuum leak 97 S10 Blazer 2wd automatic, power brake booster, vacuum leak

Question
Hi Wayne
I can hear a large vacuum leak and it takes hard pressure to bring the car to a stop.  At idle it sometimes stalls out but once it gets going it drives fine other than peddle pressure.  I found two bad vacuum lines above the power brake booster going to a small canister attached to the hood and replaced them.  (smog?) Didn't solve the problem.
I know this sounds like a bad power brake booster but I replaced it about 10,000 miles ago (perhaps in error) and the problem went away till just last week.
Thank you in advance for anything you can suggest
dave

Answer
Hi,

You need to find the vacuum leak first.  Check around the manifold and booster.  Listen up near the brake pedal for an inside leak.  Fix that leak and the booster will work. If the booster is leaking it needs a new booster.  Does the hissing change pitch when you apply the brakes? That would indicate a bad booster.

Wayne